Various methods of adjusting density in image forming are used. For example, as described in the Japanese Patent Application Publication No. 2006-79001, toner density may be adjusted when the density of a test pattern formed on a transfer belt, which may be detected by a sensor, does not fall within an acceptable density range.
However, since the acceptable density range is previously set by default, the above-described method may not be applicable to the case in which a user desires to adjust toner even when the detected toner density falls within the acceptable density range. Similarly, the above-described method may not be applicable to the case in which the user desires not to adjust toner even when the detected toner density falls outside the acceptable density range. Further, the above-described method of adjusting density does not allow the user to freely set various other adjustment conditions including, for example, time for performing density adjustment or a type of the test pattern to be formed.